Organic electroluminescent (EL) elements are advantageous, for example, in that they have high visibility by virtue of a self-luminous type, are solid state displays unlike liquid crystal displays, are less likely to be influenced by a temperature change, and have a large view angle. These advantages have recently led to a trend toward the practical use of these organic electroluminescent elements as organic electroluminescent devices such as full-color display devices, area color display devices, and lighting.
In organic electroluminescent elements, organic luminescent materials constituting the luminescent layer are classified into low molecular type and high molecular type. For example, the high molecular type luminescent layer can be formed by various printing methods or ink jet printing methods, using organic luminescent material-containing inks for a luminescent layer. For example, a method has been proposed in which a luminescent layer is formed by an offset printing method which comprises receiving a thixotropic organic luminescent material-containing ink having a viscosity of 100 to 60000 cP in a silicone blanket from an intaglio and then transferring the ink onto a substrate in a sheet form (Japanese Patent Laid-Open No. 93668/2001). Further, a method has also been proposed in which a luminescent layer is formed by an offset printing method which comprises providing an ink comprising an organic luminescent material contained in a solvent having a water solubility of not more than 5% by weight, receiving the ink in a blanket from an intaglio and then transferring the ink onto a substrate (Japanese Patent Laid-Open No. 291587/2001). Furthermore, a method has been proposed which comprises feeding an ink containing an organic luminescent material onto the surface of a silicone blanket through a gravure roll to form a coating film, pressing the coating film by a relief plate, removing the coating film in its pressed sites, and then transferring the coating film remaining on the surface of the silicone blanket onto a film forming face to form a luminescent layer (Japanese Patent Laid-Open No. 178915/2004).
Furthermore, a method has been proposed in which a luminescent layer is formed by an intaglio offset printing method which comprise providing an ink containing an organic luminescent material and a blanket formed of a silicone elastomer, which, when immersed in a solvent used in this ink, exhibits a volume change of not more than 40%, transferring the ink from the concave part in an intaglio onto the blanket, and further transferring the ink onto a substrate (Japanese Patent Laid-Open No. 308973/2003). Furthermore, a full-color or area-color display device has been proposed as an organic electroluminescent device (Japanese Patent Laid-Open No. 111158/2004). This device is formed by providing an insulating layer in a desired pattern on an anode formed substrate, forming a luminescent element layer including a luminescent layer on an electrode pattern in an insulating layer-free area (luminescence display area), and forming a cathode in a desired pattern on the insulating layer so as to contact with the luminescent element layer.